One type of signal connector, which may be an electrical or optical connector, includes a barrel that holds a body with passages that receive electrical contacts or optical termini. A coupling nut that lies around the barrel, can be turned to threadably connect the barrel to a mating connector. A mechanism is used to allow the coupling nut to turn in a direction to mate, while resisting turning in the opposite direction to unmate. Present mechanisms include a radial gear ratchet which takes up considerable radial space. Sufficient radial space can be provided without increasing the overall diameter of the connector by using thinner coupling nut walls, except that the walls then are too thin when the coupling nut is formed of plastic. A mechanism that allowed the coupling nut to turn more freely in mating than unmating and which took up little radial space would be of value.